Peak shaving gas mixing control system



July 6, 1954 x, SCHMIDT 2,682,884

PEAK SHAVING GAS MIXING CONTROL SYSTEM Filed Feb. 6, 1952 *-1 INVENTOR- 84 E wiN X.S0HM|DT TORNEY Patented July 6, 1954 PEAK SHAVING GAS MIXING CONTROL SYSTEM Edwin X. Schmidt, Nashctah, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application February 6, 1952, Serial No. 270,244

6 Claims.

This invention relates to a peak shaving gas mixing control system.

Operation of a peak shaving gas mixing plant over a. relatively long period of time on a fixed schedule of 10% or less of peak shaving gas by volume in the final gas mixture is advantageous. Such operation affords the most economical use of auxiliary gas consistent with satisfactory consumer appliance utilization. The copending Schmidt and Warner application Serial No. 652,431, filed March 6, 1946, now U. S. Patent 2,608,199, granted August 26, 1952, discloses a peak shaving gas mixing apparatus which is particularly adapted to such operation.

The present invention has as one of its primary objects to provide an improved peak shaving gas mixing plant control system affording the aforementioned type of operation.

Another object is to provide a control system which normally functions to maintain peak shaving gas mixing at a predetermined fixed volumetric basis and which functions in response to failure or deficiency of base gas supply to afford supply of peak shaving gas on a 100% or increased percentage basis and at'a heating value insuring satisfactory consumer applianceutilization, and

Another object is. to provide a systeinof the aforementioned character including 'calorimetric control and indicating means of a novel type.

Other objects and advantages of the invention will hereinafter appear. 7

The accompanying drawing illustrates a preferred embodiment. of the invention which will now be described, it being understood that the embodiment disclosed is susceptible of various modifications in respect of details without departing from the scope of the appended claims. The single figure of the drawing illustrates schematically and diagrammatically a fully automatic peak shaving gas mixing control system constructed in accordance with the invention.

Referring to the drawing, the numeralE designates a conduit through which a base gas, such as natural gas or carburated water gas, is adapted to flow. Conduit 5 is provided with a metering device in the form of a fixed orifice 6. Any suitable means (not shown) may be employed for insuring maintenance of a predetermined pressure of the base gas at the upstream side of orifice 6, whereby a predetermined lower pressure will normally be provided on the downstream side of said orificef By wayof example let it be assumed that the base gas flowing in conduit 5 has a total heating value of 540 B. t, u.

2 per cubic foot. Conduit 5 at the downstream side of orifice 6 merges with a conduit 1 which may be assumed to be connected with a distribution system.

Peak shaving gas, such as propane, may be assumed to be supplied from any suitable source (not shown) at a fixed supply pressure to a conduit 8 which is connected to conduit 1 through a conduit 9. Conduit 8 has associated therewith a by-pass conduit I0.

Air may be assumed to be supplied from any suitable source (not shown) at a fixed supply pressure to a conduit l I, which merges with conduit 9. As will be appreciated the peak shaving gas and air flowing inconcluits 8 and H mix in conduit 9 to form a peak shaving gas-air mixture which flows into conduit 1 to supplement the base gas supplied to the latter conduit.

Conduit 8 is provided with a flow control valve in the form of a butterfly valve l2 which is con nected to a piston l3, movable in a cylinder M, by the medium of linkage I5, l6 and I I. Cylinder It has connecting interiorly thereof at opposite ends the pipes l8 and I9 which terminate at open ends adjacent the end of a nozzle 29 of a ratio controller 20.

Ratio controller 28 is of the general character disclosed in the Wunsch Patent No. 1,558,529. More particularly controller 20 includes upper and lower diaphragms' 20 and 20, respectively.

The upper and lower sides of diaphragm 2t are subjected to the fluid pressure at the upstream and downstream sides, respectively, or orifice 6, through the medium of pipes 2| and 22. A member 20 rigidly connected to diaphragm 20 bears against the upper side of nozzle 20 The lower and upper sides of diaphragm 20 are subjected to the fluid pressures at the upstream and downstream sides of a restriction valve in the form of a butterfly valve 23 in conduit 8, through the medium of pipes 24 and 25, respectively. A member 20 rigidly connected to diaphragm 2w bears against the bottom side of nozzle 26 When fluid under pressure is flowing through nozzle 2% controller 20 functions to balance the pressure drop across orifice 6 against the pressure drop across valve 23, and actuates valve [2 through movement of piston H to maintain a constant ratio between these pressure drops. Thus the peak shaving gas flowing in conduit 8 is maintained in a constant volumetric ratio to the base gas flowing in conduit 5.

The volumetric ratio between the base gas and peak shaving, gas is determined by the adjustment of valve 23 through the medium of handsetting mechanism schematically depicted by numeral 26. Such hand-setting mechanism can be of any preferred form permitting adjustment of valve 23 to any selected position between closed and fully open positions.

Conduit 8 is additionally provided with a metering valve in the form of butterfly valve 21. Valve 2! is connected by suitable linkage 26, 29 and 30 to a piston 3| which moves in a cylinder 32. Cylinder 32 has connecting interiorly thereof, at opposite ends, pipes 33 and 34 which terminate at open ends adjacent the end of a nozzle 35 of a pressure drop regulator 35.

Regulator 35 is provided with a diaphragm 35 which is subjected on its lower and upper sides to the fluid pressures at the upstream and downstream sides, respectively, of valve '21, through the medium of pipes 36 and 31. A member 35 rigidly connected to diaphragm 35 bears against the bottom side of nozzle 35*. A loading spring 35 abuts at its lower end against the upper side of nozzle 35 and at its upper end bears against an abutment 35 Regulator 35 functions in response to changes in the pressure drop across valve 2'! to effect movement of piston 3! to adjust the valve 21 so that the pressure drop across the latter will be maintained constant.

Valve 2! is connected by suitable linkage 38, 39 and 49 to a corresponding metering valve in the form of a butterfly valve 4| in conduit II. The linkage 38, 39 and 49 is so arranged and proportioned that upon a given adjustment ofvalve 21 valve 4| will be given a corresponding proportional adjustment, thereby maintaining the areas of opening of valves 21 and 4| in fixed ratio.

Conduit i I is additionally provided with a flow control valve in the form of a butterfly valve 42, which is connected by suitable linkage 43, 44 and 45 to a piston 46 moving in a cylinder 41. Cylinder 4'! has connecting interiorly therewith, at opposite ends, the pipes 48 and 49 which terminate at open ends adjacent the end of a nozzle th of a pressure difference regulator 50.

Regulator 50 is provided with a diaphragm 56 which is subjected on its upper and lower sides to the fluid pressures at the upstream and downstream sides of valve 4|, respectively, through the medium of pipes 51 and 52. A member 56 rigidly secured to diaphragm 56 bears against the upper side of nozzle 5%. A spring 59 is interposed between the lower side of nozzle 56 and an adjustable abutment 56 The degree of compression of spring 5!] may be initially manually adjusted in any suitable manner to preselect the value of pressure drop valve 4|, and hence the angular position of valve 42, for any given adjustment of valve 4!. Spring 56 is subject to adjustment of its degree of compression by operation of a reversible electric motor 53, through the medium of reduction gearing 54 and an associated crank 55 to effect an increase and decrease in compression of such spring. As will be hereinafter more fully explained motor 53 is controlled by a B. t. u. controller generally designated by the encompassing broken line 56.

By-pass conduit in merges at its upstream end with conduit 8 at the upstream side of flow control valve l2 and at its downstream end with conduit 8 at a point between restriction valve 23 and metering valve 27. Conduit I6 is provided with a pressure regulator 5! having a valve seat 51 a valve plug 51 an operating stem 51 and a diaphragm 51 Stem 51 is connected to diaphragm 51 and plug 51 to move the latter relative to the seat 5'1 in response to movement of diaphragm 51 Diaphragm 5'! has a member 5'! secured to its upper surface and a pivotally supported lever 51 bears against member 51. A weight 5'! adjustably carried on lever 51 is provided to adjust the loading on the upper side of diaphragm 51 The lower side of diaphragm 5'! is subjected to the pressure of the mixed auxiliary gas and air in conduit 9 through the medium of a pipe 58.

Lever 51 of regulator 51 is adapted to engage the movable contactor of an electric switch 59 which may be assumed to be normally biased to open-circuit position. The loading of regulator 51 by weight 51 will move plug 51* down and off of seat 51 when the pressure in conduit 9 falls appreciably below a predetermined value. Under such condition switch 59 will open under its bias. It may be assumed that when the pres sure in conduit 9 exceeds said predetermined value lever 5! will assume the position depicted in the drawing'wherein it holds switch 59 in closed position against its bias.

Switch 59 has its left-hand stationary contact connected through a conductor 66 to a junction point X in an electrical network of B. t. u. controller 56. The right-hand stationary contact of switch 59 is connected to adjusting element 6i of a rheostat 6|. Rheostat 6! has a resistance element Bi which has a single end terminal 61, and said rheostat has a contact 6| adjacent but electrically isolated from the upper end of resistance element 61*. Adjusting element SP is mechanically connected to valve .23 by suitable linkage 62 62 and 62, through the medium of which it is adapted to be positioned on resistance element 6| in accordance with the adjustment selected for valve 23. Terminal 6| of resistance element 6! is connected through a resistor 63, and normally closed contacts 64 of a switch 64 to the right hand terminal of the resistance element 65* of a potentiometer rheostat 65 of controller 56.

B. t. u. controller 55 is similar to that shown in the Schmidt Patent No. 2,238,606, issued April 15, 1941. Controller 56 has associated therewith a calorimetric device 66, which may be assumed to be of the type shown in the aforementioned patent. Calorimetric device 66 is supplied with a continuous sample of the peak shaving gas-air mixture flowing in conduit 9 through the medium of a pipe 61.

The left-hand terminal of the resistance element 65 of rheostat 65 is connected in series with a resistor 68 to junction point X and said resistance element has its right-hand terminal connected in series with a tank temperature compensatin resistor RT, located in calorimetric device 66, a resistor 69, the resistance element Ell of a potentiometer rheostat 10, a battery H and a variable resistor I2. A resistor 13 is connected between junction point X and the point common between resistor RT and resistor 69.

calorimetric device 66 is provided with an electro-thermocouple 14 comprising series connected cold and hot junctions CJ and HJ. Junction HJ is connected in series with the contacts 64 of switch 64, galvanometer G, and contacts 64 of said switch to the adjusting element 65 of potentiometer rheostat 65. Junction CJ is connected to ground and to junction point X.

The point common between the right-hand contact of contacts 64 and galvanometer G is connectable through contacts 15* of a switch 15 to junction point X. The point common between galvanometer G and the right-hand contact of contacts 64 is connectable through contact of switch 15 and a standard cell SC to adjusting element 10* of rheostat It. Switches 64 and I5 are mechanically interlocked through a pivoted toggle lever l6 so that when switch 64 is closed switch'l5 is open and vice versa.

Galvanometer G is mechanically connected to adjusting element 55 of rheostat 65 and said adjusting element is mechanically coupled to the movable contactor Ti of a switch 1! which has a pair of stationary contacts Tl and 11. The arrangement is such that deflection of galvanometer G to either side of its neutral point will cause corresponding movement of adjusting element '35 and contactor H In practice galvanometer G would not actually afford the drive, but control the device afforded drive from an auxiliary driving source as shown and described in the aforementioned Schmidt patent.

The aforementioned reversible motor 53 is connectable to a supply line L of an electrical switch through a normally open switch it which is periodically closed through the medium of a rotating cam 19 driven by a motor 88 connected across supply lines L and L of said supply circuit. Contactor (T of switch 1! is connected to line L and contacts 11 and 11 are connected to terminals T and T respectively, of motor 53. Motor 53 has a terminal T directly connected to supply line L Let it be assumed that with a base gas consisting of carburated water gas being supplied to conduit 5 at a preselected supply pressure that it is desired to mix with it peak shaving gas, consisting of a propane-air mixture, in such proproportional to the flow of base gas at alltimes.

Pressure difference regulator 35 will function to maintain a constant pressure drop across metering valve 21. Valve 4! in air conduit II will be opened to the same degree as valve 21 so that the ratio of areas of opening of valves 2! and 4! rer main constant. Controller 56 functions to adjust flow control valve i2 so that the flow of air in conduit II will produce a pressure drop across valve 4| depending on the loading of spring 56. With this loading fixed, flow of peak shaving gas through valve 2! and flow of air through valve 4| will then remain in fixed proportion. Changing the loading of spring 56 changes the ratio of flows and the heating value of the mixture in conduit 9. If the pressure of the mixed gas flowing in conduit 1 is above a predetermined pressure, pressure regulator 57 will assume the valve closed condition depicted in the drawing and switch 59 will be closed as depicted.

With switch 59 closed, and valve 23 set for 10% or less peak shaving, contact (it will be in contact with terminal 8!, and with contact 54 closed, resistor 63 will be connected across resistor 68 and potentiometer $5, to thereby reduce the current fiow through and the potentials across resistors 63 and 65. With valve 23 set for over ten per cent peak shaving, portions of rheostat 6| are included with resistor 63 in this parallel circuit reducing the potential across resistors 68 and 65 to a lesser extent. Resistance values of rheostat BI and 63 are selected so that the potential across resistors 68 and 65 are propor tional to the value of heating value of the peak shaving mixture which will not cause problems in the utilization of the mixture of peak shaving gas and base gas. Thus, at 10% or less peak shaving, this potential would be equal to the potential generated by thermocouple 14 when the heating value of gas in conduit 9 had a heating value equal to that of the base gas. With valve 23 set for higher percentage of peak shaving, rheostat Bl might be in the position shown with sec- El to El included in the circuit, requiring a higher potential from thermocouple M to maintain slider 65* at the control point.

The E. M. F. of thermocouple M in calorimetric device 66 of course varies in a well known manher in accordance with the variation in B. t. u. content of the auxiliary gas-air mixture supplied through sampling pipe 67. Change in E. M. F. of thermocouple Hi effects an unbalance in the potentials to which galvanometer G in controller 56 is subjected and its movable element (not shown) moves from its neutral position and effects a corresponding movement of adjusting element of rheostat and contactor H of switch ill from their respective balance and center positions, which may be assumed to be those depicted in the drawing. Contactor ll when so moved engages with either contact Ti or ll, depending upon the direction of move-- ment of the movable element in galvanometer When contactor Il engages with contact il' circuit connections are thereby established for motor 53 to afford operation of the latter in one direction in small increments of rotation in response to the periodic closure of switch 4'8 by cam 19 which may be assumed to be continuously driven by motor 80. Similarly," when contactor it' en gages with contact 77 circuit connections are thereby established for motor 53 enabling its operation in the reverse direction in small increments of rotation under the control of switch i8.

Operation of motor 53, as aforeindicated, effects a readjustment of the tension of spring 56 in controller 59 so that the latter will thereafter function to afford a different degree of opening of valve lz for the same degree opening of valve M. Such change in degree of opening of valve 62 changes the volumetric proportion of air in the auxiliary gas-air mixture flowing in conduit 9, thereby effecting an increase or decrease in the heating value of such mixture as the case may be.

When the heating value of the adjusted auxiliary gas-air 'mixture approaches the value which controller 56 is set to maintain, the potentials to which galvanometer G is subjected approach a balance and when ultimately balanced the movable element of the galvanometer again attains its neutral position and adjusting element 65 of rheostat 65 and contactor 'll of switch 71 to attain their respective balance and center positions as depicted in the drawing. As

- a result, operation of motor 53 ceases until a condition of potential unbalance in galvanometer G again occurs.

The foregoing description of operation of course does not indicate the manner of functioning of the aforedescribed potentiometer circuit of controller 56. For a more complete under standing of how controller 56 functions reference should be made to the aforementioned Schmidt patent.

The aforedescribed condition of operation of the system presupposes that the contacts of switch 64 are closed and that the contacts of switch 15 are open as depicted in the drawing. Closing of the contacts of switch 15 and opening of the contacts of switch 64 enables calibration of controller 56 and adjustment to compensate for deterioration of battery II as is fully explained in the aforementioned Schmidt patent. It will be noted that opening of switch contacts insures that adjustable rheostat BI and resistor 63 will be disconnected from circuit regardless of the positioning of switch 59.

If during operation of the system the supply of base gas should completely fail, or fall to a very low value, pressure regulator 51 will respond to move to valve open position thereby opening by-pass conduit I around valves l2 and 23, and also effecting opening of switch 58. Opening of switch 59 efiects disconnection of rheostat SI and resistor 63 from the potentiometer circuit of controller 56.

When rheostat BI and. resistor 63 are disconnected from the potentiometer circuit of controller 56 the latter functions to maintain a higher heating value of the auxiliary gas-air mixture flowing in conduit 9. In other words, the efiective control point of the controller is increased. Thus assuming that the controller before opening of switch 59 was functioning to maintain the auxiliary gas-air mixture at 540 B. t. u./cu.ft., with such mixture comprising 10% by volume of the base gas-peak shaving gas mixture flowing in conduit 1, controller 56 will function upon opening of switch 59 to maintain the heating value of the auxiliary gas-air mixture at '700 B. t. u./cu.ft. As indicated in the aforementioned Schmidt and Warner patent, when the gas supplied to consumer appliances consists of 100% peak shaving gas the latter must have a heating value of 700 B. t. u./cu.-ft. to insure satisfactory appliance utilization. Peak shaving at this latter heating value at less than 100% peak shaving is objectionable only due to economic consideration.

Thus controller 56 should be calibrated to maintain a heating value of 700 B. t. u./cu.-ft. with switch 59 open, assuming a base gas comprising carburated water gas with a heating value of 540 B. t. u./cu.-ft., and an auxiliary gas comprising propane having a heating value of 2500 B. t. u./cu.-ft. If other base gas, such natural gas, is used, then the use of propane as the auxiliary gas requires that the control point of controller 56 be set to maintain a higher heating value, depending upon known interchangeability factors.

With switch 59 closed, controller 59 will then function to maintain a heating value of the auxiliary gas-air mixture flowing in conduit 9 at a lower value as determined by what portion of re sistance element Gi of rheostat 6| is eifectively in circuit. The position of resistance element 6 5 which will be effectively in circuit is of course determined by the adjustment of adjusting element M which is in turn determined by the adjustment of valve 23. Under normal conditions with supply of peak shaving gas scheduled on a basis of by volume of the base gaspeak shaving gas mixture and with restriction valve 23 set to afford such proportion, adjusting element 6| should be set to afford inclusion of that amount of resistance element Bi which together in series with resistor 63 will cause controller 56 to function to maintain a heating value of the auxiliary gas-air mixture flowing in con- .8 duit 9 at the heating value of the base gas. As will be appreciated when the mixing of peak shaving gas is scheduled on a higher proportion than 10% by volume of the resultant base gaspeak shaving gas mixture, restriction valve 23 will be opened to a further degree. Correspondingly adjusting element Bl of rheostat iii, through the medium of linkage 62, 63 and 8 will be adjusted to include a greater amount of resistance element 6| in circuit with the potentiometer circuit of controller 55, thereby effecting a corresponding increase in heating value of the auxiliary gas-air mixture which controller 56 will be set to maintain.

in order to stabilize potentiometer current independent of the condition of the parallel circuit including switch 59, rheostat 6i and resistor a switch 64 is included in this circuit. Switch 64- is part of standardizing switch 69 which is mechanically coupled to switch 15. In the drawing these switches are shown in the operating position. In the standardizing position 64 is opened and 15 closed. Galvanometer G is then connected in series with standard cell SC, the left hand portion of resistor element 79 of potentiometer T6 and resistor 69 across resistor l3, and such series connected combination is also in parallel with the series combination of resistor RT, resistance element 65 of potentiometer 65 and resistor 68, which latter series combination is likewise connected across resistor 13. The circuit including resistors 93 and El is open circuited by switch 64 Battery rheostat l2 may then be adjusted to balance standard cell voltage against the voltage drop across this circuit as fully described in the aforementioned Schmidt patent, the setting of 70 being adjusted to produce balance of 65 at the control point when the heating value of the peak shaving mixture is at the correct value for 100% replacement of base gas.

The system further comprises a potentiometer circuit 84 forming part of a heating value recorder. This circuit is similar to the circuit described in Schmidt patent and operates on the same thermocouple 74 forming part of calorimeter 66. A thermometer RT forming part of the circuit is included in calorimeter 88. Arm 8? or potentiometer is mechanically connected to an indicator and recording pen (not shown) to give an indication and record of peak shaving mix-- ture heating value.

The system further comprises a potentiometer circuit 84 for control of a B. t. u. recorder (not shown). This potentiometer circuit, which is in certain respects similar to that aforedescribed in connection with controller 56 will now be described.

A resistor 85 is connected at its left-hand end through a conductor 85 to the point common to cold junction CJ of thermocouple i l and the ground to which said junction is connected. Resistor 85 is connected at its right-hand end in series with resistance element di of a potentiometer rheostat 87, a compensating thermometer resistor ET in calorimetric device 05. anti a resistor 88 to junction Z which is common to conductor 86 and its aforementioned left-hand. A resistor 89 is connected at its left-hand end to the point common between resistor RT and resistor 88, and its right-hand end is connected series with resistance element 9% of a potentiometer rheostat 99, a battery 95, and an adjustable resistor 92 to junction point Z. A galvanometer G is connected at its left-hand side in series with normally closed contacts 93 of switch 93 to the point common between hot junction HJ of thermocouple 14 in calorimetric device 66 and the left-hand contact of contacts 64 of switch 64. Galvanometer G is connected at its righthand side in series with normally closed contacts 93 of rheostat 93% to adjusting element 81* of rheostat 81. The point common between the right-hand contact of contacts 93 and galvanometer G i connectable through normally open contacts 94* of a switch 94 to conductor :86. The point common between the right-hand contact of contacts93 and galvanometer G is connectable through normally open contacts 3 1* of switch 94, and in series with a standard cell SC to adjusting element 90 of rheos'tat 99.

Switches 93 and 9d are mechanically interlocked, as schematically depicted by the pivoted toggle lever 95, so that when switch 93 is closed switch 94 is open and vice versa;

Galvanometer G? may be assumed to have a movable element (not shown) which is deflected to either side of itsne'utral position in response to variations in E. M. F. of thermocouple i l in a manner similar to that aforedescrlbed in connection with galvanometer G of controller 55. Thus a recording device, such as shown in the aforementioned Schmidt patent can be controlled so that a continuous record of instantaneous variations in heating value of the auxiliary gasair mixture flowing in conduit 9 will be had.

I claim:

1. In a system for mixing a base gas and a supplementary gas in fixed preselected volumetric proportions, the combination with means affording flow of a base gas and a supplementary gas, of means responsive to variationsin the rate of flow of base gas to maintain the flowof supplementary gas in a preselected volumetric proportion to the flow of base gas, calorimetric means responsive to variations in heating value of the supplementary gas, control means associated with said calorimeteric means normally acting to maintain the heating value of the supplementary gas at a given value, means including pressure responsive means for effecting an increase in the volumetric proportionality of the supplementary gas to base gas when the supply of base gas and the preselected proportion of supplementary gas fails to meet the demand, and means under the control of said pressure responsive means for causing said control means to thereafter maintain the heating value of the supplementary gas at another given higher value.

2. In a system for mixing a base gas and a peak shaving gas in a fixed preselected volumetric proportion, the combination with means affording flow of a base gas and a peak shaving gas, of means responsive to variations in the rate of flow of base gas to maintain the flow of peak shaving gas in a preselected volumetric proportion to the flow of base gas, calorimetric means responsive to variations in heating value of the peak shaving gas, control means under the direction of said calorimetric means normally acting to maintain the heating value of the peak shaving gas at the same value as that'of the base gas, means including pressure responsive means for effecting increase in the volumetric proportionality of peak shaving gas to base gas when the supply of base gas and the preselected proportion of peak shaving gas fails to meet the demand, and means under the control of said pressure responsive means for causing said control means to thereafter maintain the heating value of the peak 10 shaving gas at that value required for satisfactory appliance utilization when supplied with peak shaving gas. I

3. In a system for mixing a base gas and a supplementary gas in a fixed preselected volumetric proportion, in combination, means afford ing supply and flow of a base gas, means for effecting flow and mixing of a peak shaving gas and air comprising a conduit affording flow of peak shaving gas, means including valve means in said conduit responsive to variations in the rate of flow of base gas to maintain the flow of peak shaving gas in a preselected volumetric proportion to that of the base gas, a second conduit affording flow of air, means including a bypass conduit section around said valve means and a pressure responsive valve normally closing said conduit section whenever the pressure of the peak shaving gas-air mixture is above a given value and responding to decrease in pressure below said given value to open said conduit section and afford now of peak shaving gas at an increased volumetric rate and means including valve means in said second conduit for normally maintaining the flow of air in constant volumetric proportion to that of the peak shaving gas, and means for controlling the heating value of the peak shaving gas-air mixture comprising calorimetric means continuously subjected to the peak shaving gas-air mixture, additional valve means in said second conduit controlled by said calorimetric means to afford. change in the volumetric proportion of air to that of the peak shaving gas in accordance with instantaneous changes in the heating value of the peak shaving gas-air mixture and means under the control of said pressure responsive valve normally conditioning said calorimetric means to maintain the heating value of the peak shaving gas-air mixture at a given value whenever said conduit section is closed and affording in response to opening of said conduit section conditioning of said calorimetric means to maintain the heating value of the peak shaving gas-air mixture at another given higher value.

4. In a system for mixing a base gas and a liquid petroleum gas-air mixture in a fixed preselected volumetric proportion, in combination, means affording supply and flow of a base gas, means for effecting flow and mixing of a liquid petroleum gas and air comprising a conduit affording flow of 'a liquid petroleum gas, means including valve means in said conduit responsive to variations in rate of flow of base gas to maintain the flow of petroleum gas in a preselected volumetric proportion to that of said base gas, a second conduitaffording flow of air, means including valve means in said second conduit responsive to variations in rate of flow of petroleum gas to normally maintain the flow of air in that volumetric proportion to the petroleum gas as will afford the same heating value of the petroleum gas-air mixture as that of said base gas, means including a bypass conduit section around the valve means in the first mentioned conduit and a pressure responsive valve normally closing said conduit section whenever the pressure of the petroleum gas-air mixture is above a given value and responding to decrease in pressure of the latter mixture below said given value to open said conduit section to afford increased volumetric rate of flow of petroleum gas, and means for controlling the heating value of the petroleum gas-air mixture comprising calorimetric means continuously subjected to the petroleum gas-air mixture, additional valve means in said second conduit controlled by said calorimetric means to afford change in the volumetric pro ortion of air to that of the petroleum gas in accordance with instantaneous variations in the heating value of the latter mixture and means under the control of said pressure responsive valve normally conditioning said calorimetric means to maintain the heating value of the petroleum gas-air mixture at the aforementioned value whenever said conduit section is closed and afiording in response to opening of said conduit section conditioning of said calorimetric means to thereafter maintain the heating value of the petroleum gas-air mixture at that value required for satisfactory appliance utilization when supplied with 100% petroleum gas-air mixture by volume.

5. In a system for mixing a base gas and a supplementary gas in a fixed preselected volumetric proportion, in combination, means affording supply and flow of a base gas, means for effecting fiow and mixing of an auxiliary gas and air comprising a conduit affording flow of an auxiliary gas, a second conduit affording flow of air, means responsive to variations in the rate of flow of base gas including a valve in the first mentioned conduit and a fixed but adjustable valve in said first mentioned conduit for maintaining flow of auxiliary gas in a preselected volumetric proportion to that of the base gas, means including a conduit section providing a by-pass around the first mentioned and adjustable valves in the first mentioned conduit and a pressure responsive valve acting to maintain said conduit section closed whenever the pressure of the auxiliary gas-air mixture is above a given value and responding to decrease in pressure of the auxiliary gas-air mixture below the aforementioned value to open said conduit section to provide increased rate of flow of auxiliary gas and means responsive to variations in the rate of fiow of auxiliary gas including a third valve in said first mentioned conduit and a fourth valve in said second conduit for normally maintaining the flow of air in a preselected constant volumetric proportion to that of said auxiliary gas, and means for controlling the heating value per unit volume of the auxiliary gas-air mixture comprising a fifth valve in said second conduit, a regulator having control point adjusting means and being responsive to variations in pressure drop across said fourth valve for controlling the adjustment of said fifth valve, calorimetric means continuously subjected to the auxiliary gas-air mixture and responding to instantaneous variations in heating value thereof to effect through the medium of said control point adjusting means readjustment of the control point of said regulator and means subject to control by said pressure responsive valve normally conditioning said calorimetric means for maintaining a preselected heating value of the auxiliary gas-air mixture Whenever said by-pass conduit section is closed and affording in response to opening of said by-pass conduit a predetermined increase in heating value of the auxiliary gas-air mixture thereafter maintained by said calorimetric means.

6. In a system for mixing a base gas and a supplementary gas in a fixed preselected volumetric proportion, in combination, means affording supply and flow of a base gas means for effect ng flow and mixing of an auxiliary gas and air comprising a conduit affording fiow of an auxiliary gas, a second conduit afiording flow of air, means responsive to variations in the rate of flow of base gas including a valve in the first mentioned conduit and a fixed but adjustable valve in said first mentioned conduit for maintaining flow of auxiliary gas in a preselected volumetric proportion to the base gas, means inclu-ding a conduit section providing a by-pass around the first mentioned and adjustable valves in the first mentioned conduit and a pressure responsive valve acting to maintain said conduit section closed whenever the pressure of the auxiliary gas-air mixture is above a given value and responding to decrease in pressure of the auxiliary gas-air mixture below the aforementioned value to open said conduit section to provide increased rate of fiow of auxiliary gas and means responsive to variations in rate of flow of auxiliary gas including a third valve in the first men tioned conduit and a fourth valve in said second conduit for maintaining the fiow of air in constant volumetric proportion to that of said auxiliary gas, a fifth valve in said second conduit, a regulator responsive to variations in pressure drop across said fourth valve to eifect adjustment of said fifth valve and having control part adjusting means under the control of an electric motor, calorimetric means responsive to variations in heating value of the auxiliary gas-air mixture comprising a measuring circuit including a potentiometer type rheostat having its adjusting element positioned in accordance with changes in the heating value of the auxiliary gas-air mixture and switch means under the control of the rheostat adjusting element for controlling the operation of said electric motor, a resistor, and means including a switch under the control of said pressure responsive valve for connecting said resistor in parallel with said rheostat whenever the by-pass conduit section is closed to normally condition said calorimetric means for maintaining a given heating value of the auxiliary gas-air mixture, said switch upon opening of said by-pass conduit section affording disconnection of said resistor to thereby condition said calorimetric means to thereafter maintain a preselected higher heating value of the auxiliary gas-air mixture.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,858,689 Smoot May 17, 1932 2,248,606 Schmidt Apr. 15, 1941 2,349,517 Pinkerton May 23, 1944 2,349,521 Schmidt May 23, 1944 2,399,830 Schmidt May 7, 1946 2,608,199 Schmidt Aug. 6, 1952 

